1. Field
The technology of the present application relates generally to intraoperative monitoring (IOM), and more specifically, to garments and methods of using the garments to facilitate placement of needle or surface electrodes for IOM.
2. Background
During surgery, nerve damage is possible for a number of reasons. For example, one potential complication from surgery may include peripheral neuropathy related to surgical positioning that may in some cases be generally known as an iatrogenic injury. Intraoperative positioning nerve injuries are complications from surgery that may occur from extension or compression of peripheral nerves.
Nerve injuries may be preventable by monitoring nerves or muscle groups innervated by the nerves for degradation of conductivity or the like. Even though preventable in many instances, peripheral nerve injuries still occur during surgery.
Because positioning injuries occur, some surgeries include intraoperative monitoring (“IOM”). The goal of IOM is to identify changes in brain, spinal cord, and peripheral nerve function prior to irreversible damage occurring.
IOM typically includes using an evoked potential such as, for example, somatosensory evoked potentials (SSEP), brain stem auditory evoked potentials (BAEP), motor evoked potentials (MEP), and visual evoked potentials (VEP). Generally, the activity associated with evoked potentials are elicited/evoked from a time-locked peripheral stimulus, such as, for example, stimulus to the arms/legs for SEP, noise in the ear for BAEP, or light for VEPs. Electromyography (EMG) recording of induced or mechanical muscle activation is also is used extensively during operative cases. Scalp electroencephalography (EEG) provides data for analysis of more spontaneous global electrocortical activity. Scalp EEG also can be used to monitor cerebral function during carotid or other vascular surgery. In addition, EEG recorded directly from the pial surface, or electrocorticography (ECoG), is used to help determine resection margins for epilepsy surgery, and to monitor for seizures during electrical stimulation of the brain carried out while mapping cortical function.
Looking specifically at SSEP, SSEPs are recorded by stimulating peripheral afferent nerves, usually electrically, and the responses are recorded with the help of scalp electrodes. Because of the presence of nonspecific EEG background activity, the evoked potential must be time-locked to the stimulus and averaged to improve signal-to-noise ratio.
In intraoperative use, the median, or ulnar nerves, at the wrist are the most common stimulation site for upper extremity monitoring. In the lower extremity, the posterior tibial nerve just posterior to the medial malleolus, or common peroneal at the politeal fossa, are used most commonly. Alternative sites of stimulation along the path of the peripheral nervous system also may be used.
Needle electrodes generally are used as they are easier to apply than, for example, surface electrodes that would require the skin to be prepared prior to use. Recording electrodes are placed on the scalp over the correlate sensory cortical areas and over the lumbar and cervical spine. Additionally, electrodes can be placed at the Erb's point for upper extremity SSEP recording and over the politeal fossa for lower extremity recording. A correlation to Erb's point for lower extremity is the popliteal fossa at the back of the knee. The readings are to confirm that stimulus is being delivered.
FIG. 1 shows a typical measure SSEP waveform 100. Waveform 100 is known as an N20 waveform and relates to the negative peak of the potential occurring at approximately 20 milliseconds. The waveform 100 was generated by a peripheral nerve stimulator using a constant current stimulus output applied to the wrist of a patient. Other types of stimulators are possible as well, such as, for example, a voltage based stimulator, a magnetic based stimulator, etc. The waveform 100 was the measured response by an electrode placed on the skin surface or subdermally of the patient's head. In this case, an electrode 200 was placed about 4 cm up and 2 cm back from the top of the ear 202 of the patient 204 as shown in FIG. 2.
As can be appreciated, placement of the electrodes in the patient is a part of IOM. A certified or skilled 10M technician must be on-site in the operating room to insert the needle electrodes properly into the patient using conventional methodologies. The on-site skilled 10M technician increases the cost of IOM and often results in many surgeries being conducted without IOM due to their cost and lack of availability in some areas. In some instances, nerve injury may be prevented if IOM had been available. Therefore, there is a need in the art for devices, apparatuses, methods, and the like to facilitate placement of needle electrodes in IOM.